This invention relates to a method and apparatus for attaching hoses and tubes to a fitting and more particularly to a specially configured, hand assembled, tube coupling and apparatus.
Attaching hoses and tubes to fittings to form a reliable fluid-tight coupling has presented problems over the years. Two basic problems are axial pull off (separation of the hose from the fitting) and pressure or vacuum sealing of a confined media. Hose clamps, crimped on ferrules, and attachments that screw on and in the hose can provide an effective method of terminating a hose but they can be complex, expensive to manufacture, and involve special tools to assemble.
A fitting having both conical and double-conical shapes (i.e., diamond shaped) in combination with a frusto-conical locking sleeve have been used to terminate a hose. Generally, the hose is thrust over the large diameter of the cone and seated about the reverse tapered portion thereof. For one reason or another this type of hose coupling has not been totally reliable and this is not generally used commercially. For example, to resist axial pull off prior, terminations have made the angle of the reverse taper greater than needed. When a hose is thick or its material is stiff and unyielding, advancing the outer sleeve by hand is so difficult that the result is inadequate pressure exerted on the hose by the outer sleeve.
To improve the hose connection utilizing the double conical fitting, it has been believed by others in the art that special arrangements are required for driving the sleeve relative to the fitting. Deutsches Reich 424980 (1926) provides a spring for driving an interiorly threaded sleeve onto the hose. These threads are at a different taper than that of the sleeve or fitting and bite into the outside of the hose to compress the sleeve about the hose and the hose about the fitting, thereby retarding loosening or pull-off of the hose from the fitting. Dutch Patent No. 27183 (1932) provides a coupling nut which is threadably advanced about the sleeve in a direction that drives the outer sleeve up onto the fitting and about the hose to increase the pressure between the hose and fitting.
The angle range is particularly important because the mechanical advantage of the sleeve capability decreases with increasing angle. When one uses a separate driving nut, one only has the mechanical advantage of the thread at initial installation or retightening.
It would be desirable to provide a coupling wherein a threadless outer sleeve could be easily set or engaged by hand, thereby eliminating the possible need for torquing the outer sleeve. With a proper angle range only very rudimentary means of preventing tube or hose "push back" or sleeve securement are required.
Accordingly, there is provided herein a hose coupling for terminating the end of a deformable hose or tubular member, which coupling includes a tubular fitting having an exterior surface and adapted to be received interiorly of the hose and a frusto-conical locking sleeve having an interior surface and adapted to be circumposed about the hose whereby the hose is clampingly secured between the surfaces of the fitting and sleeve. Further, the fitting includes a forwardly extending frusto-conical portion which defines a lead-on area at the end of the fitting. In particular, the hose engaging surfaces are frusto-conical with the angles defining each cone being limited to a narrow specified range. In accordance with this invention the frusto-conical surfaces are defined by a taper angle of between 1/2 degree to 4 degrees per side relative to the fitting axis. (i.e., the frusto-conical surfaces define a 1.degree. to 8.degree. double included angle.)
The prior art fails to recognize that the included conical angle of the hose engaging surfaces be small and be from about 1/2 degree per side to 4 degrees per side. Unexpectedly, this specific angle range produces locking and sealing results that are so outstanding that threads and springs, etc., are not necessary for the same reliability. Selection of the special angle range resists any relative movement of between the sleeve, hose, and fitting that could loosen the mechanical lock on the reverse taper or disrupt the pressure sealing integrity of the attachment. A fitting so configured allows the use of an outer sleeve that is very simple, requires only minimal force to compress the hose about the fitting, and is spaced away from the hose sealing area yet provides an additional locking of the hose to the exterior of the fitting. All of this may be accomplished by hand setting of the outer sleeve.
It is believed that if the angle defining the frusto-conical sealing portion is greater than the above-noted specific range, very minor distortions of wall thickness will result in greater loss of sealing. Since the reliability of the attachment is also determined by how well it seals over time, angles larger than those specified herein are believed to cause a more rapid deterioration of sealing. Also, these larger angles require more distortion of the hose or tube material by what is termed secondary locking means that are incorporated on the inner member. The more rapid deterioration of the tube or hose material that results also contributes to rapid loss of sealing.
Further, in accordance with this invention, there are disclosed intermediate adapter elements between the locking sleeve and hose and/or between the hose and fitting. Specific of these elements are not wedge shaped but are also defined on their interior and exterior surfaces by the same double included angle of between 1 and 8 degrees, whereby to follow the respective interior surface of the locking sleeve or exterior surface of the fitting. The purpose of these adapter elements is to distribute stresses and assist in sealing, each typically being of a suitable elastomer. An advantage of reducing stresses is an increase in hose life.
Accordingly, there is provided herein a hose coupling including a frusto-conical fitting and sleeve lock which cooperate to resist pull off as well as having (a) resistance to the temperature caused changes that result in loosening or leaks, (b) resistance to the vibration caused changes that result in loosening or leaks, and (c) resistance to mechanical forces that push on the tube or hose in a manner that "unlocks" the sleeve lock, or encourages leaking.
The interaction of all these factors generally stems from the fact that the hose or tube is spring like, and depending on its mass and/or deformation recovery characteristics, the hose or tube will exhibit resonances of mechanical motion. One component of this mechanical movement are forces developed in an axial direction which tend to unlock this type of attachment. Temperature effects affect the resistance to these and other unlocking mechanical forces.
Advantageously, the specially configured outer sleeve fitting provide a low cost coupling, and the labor expended in "setting" the outer sleeve is definitely lower cost than setting clamps, crimping ferrules, or screw-over type attachments used in some cases to replace crimped ferrules .